The simplest jet engine is a valveless pulsating unit. After its invention, it became obvious that it could move a rocket even in the middle. Due to the fact that they began to use it everywhere, the development of the type of propulsion in question was suspended. But many amateurs continue to be interested, study and even assemble the unit themselves. Let's try to make a jet engine with our own hands.

Motor based on Lokved's patent

The device can be built of any size if you strictly follow required proportions. made with your own hands, there will be no moving parts. It is capable of operating on any type of fuel if a device is provided for its evaporation before entering the combustion chamber. However, the start is made on gas, since this type of fuel is much more convenient than others. It’s easy to build the structure, and it won’t take much money. But you need to prepare for the fact that the jet engine will operate with a lot of noise.

I also install an evaporative atomizer for liquid fuel with my own hands. It is placed at the end of a metal pipe through which propane enters the combustion chamber. However, if you plan to use only gas, then this device is not necessary to install. You can simply run propane through a 4 mm diameter tube. It is attached to the combustion chamber using a ten millimeter fitting. Sometimes they also provide different tubes for propane, kerosene and diesel fuel.

At the start, gas enters the combustion chamber, and when the first spark occurs, the engine starts. It is not difficult to purchase cylinders today. Convenient is, for example, having eleven kilograms of fuel. If a large flow rate is expected, the reducer will not provide the necessary flow. Therefore, in such cases, simply install a needle valve. In this case, the cylinder cannot be completely emptied. Then there will be no fire in the tube.

To install a spark plug, a special hole must be provided in the combustion chamber. It can be made using a lathe. The body is made from of stainless steel.

Reinsta: necessary details

It is not necessary to use metal pipes and other parts that are complicated for the average person. If you plan to make a jet engine with your own hands completely small size, for its manufacture you will need the following available components:

• four hundred milliliter glass jar;
• a tin can of condensed milk, of which only the side part is required;
• alcohol or acetone;
• compass;
• scissors;
• Dremel or regular awl;
• pliers;
• pencil;
• paper.

How to make a jet engine

In the cover from glass jar make a hole twelve millimeters.

To layout the diffuser, draw a template on paper using a compass. The near radius is taken to be 6, and the far radius is taken to be 10.5 centimeters. Measure 6 cm from the resulting sector. Trimming is done at the near radius.

The template is applied to a tin can, traced and the required piece is cut out. Both edges are folded back a millimeter at the resulting part. Next, make a cone and connect the parts of the bent edges. This is how you get a diffuser.

Then four holes are drilled on its narrow half. The same is repeated on the lid around the hole made earlier. Using wire, hang the diffuser under the hole in the cover. The distance to the top edge should be approximately 5 to 5 mm.

All that remains is to pour alcohol or acetone into the jar half a centimeter from the bottom, close the jar and light the alcohol with a match.

Miniature pulse jet engines for model aircraft can also be made independently. Even today, some hobbyists use literature written in Soviet time, in the sixties of the last century. Despite such a significant period of time since its publication, it continues to be relevant and can help young designers acquire new knowledge and gain practice.

I'm building a model that simulates a real mini jet engine, even if my version is electric. In fact, everything is simple and anyone can build a jet engine with their own hands at home.

The way I designed and built a homemade jet engine is not... The best way do it. I can imagine a million ways and schemes how to create best model, more realistic, more reliable and easier to manufacture. But now I've put together one.

Main parts of model jet engine:

• Engine direct current strong enough and at least 12 volts
• A DC source of at least 12 volts (depending on what kind of DC motor you have).
• A rheostat, the same one sold for adjusting the brightness of light bulbs.
• A gearbox with a flywheel is found in many car toys. It's best if the gear housing is made of metal because plastic can melt at such high speeds.
• A sheet of metal that can be cut to make fan blades.
• Ammeter or voltmeter.
• Potentiometer at approximately 50K.
• Electromagnet coil from a solenoid or any other source.
• 4 diodes.
• 2 or 4 permanent magnet.
• Cardboard to assemble a body similar to a jet engine body.
• Filler for car bodies, to create an exterior.
• Rigid wire to support everything. I usually use wires from cheap hangers. They are strong enough and flexible enough to be molded into the desired shape.
• Glue. For most parts I prefer hot glue, but now almost any glue will do.
• White, silver and black paint.

Step 1: Attach the DC Motor to the Transmission Flywheel

The basis of my jet engine model is very simple. Connect the DC motor to the gearbox. The idea is that the motor drives the part of the gearbox that was attached to the wheels of the toy car. Place the plastic lever so it hits the small flywheel gear and it makes noise. Some transmissions are already equipped with this device, and some are not.

Step 2: Connect the magnets and the sensor coil

Place 2 or 4 permanent magnets on the main shaft so that the coil can be near them when they rotate. Place them so that the polarity pattern is - + - +. The idea is that the magnets will pass close to the coil and generate a small amount of current, which we will use to move the sensor. But for this to work you need to put 4 diodes in a bridge configuration to convert alternating current, which we generate, into a constant.

Google "diode bridge" to find about it more information. Also, to calibrate the sensor to the desired sensitivity, you need to place a potentiometer between the coil and the sensor.

Step 3: Rheostat for speed control

We need to control the engine speed. To do this, place a rheostat between the outlet and the power source. If you don't know how to do this, Google how to connect a rheostat to light bulbs. But instead of a light bulb we will put a power supply.

Don't try this unless you are 100% sure. We are dealing with a large current and using an inappropriate power source can damage it. The simpler the power supply, the better. The alternative is to find a DC rheostat so that we can control the voltage after power is applied. I couldn't find one in any store, so I use a rheostat for light bulbs. But if you can find one that will work with a DC motor, then go for it. The idea is to simply control how much current is supplied to the motor, so this will be our inductor.

Step 4: Fan

You can make the fan the way you want. I cut each blade from thin metal sheet and glued them together. You can make them from cardboard and then paint them. Or, if you have access to a 3D printer, you can 3D print a fan. www.thingiverse.com has some great 3D models of fans.

Step 5: Body

You can make the body out of cardboard and then add external filler to give it shape. You'll have to do a lot of sanding, so it's hard and messy work. Once everything is smooth, paint the body with gloss white paint.

The inside of the engine should be painted black. The front of the engine usually has a silver edge that you can paint on if you wish.

Step 6: Starter Mechanism

The starter and fuel handles are mechanically connected. The starter has a switch that connects the engine to the power source. This switch can also be activated by the fuel control lever when it is in the operating position.

The starter spring must be loaded such that it wants to return to its normal position and will only lock the starting position if the fuel control lever is in the disengaged position.

The idea is that the starter will remain in the original position until you move the fuel lever to the run position, and the fuel control lever will now hold the switch engaged. Also the fuel lever is part of the rheostat base. The rheostat must be installed in such a way that it is possible to rotate not only the part of the handle that is supposed to rotate, but also the entire base of the rheostat. This base is what the fuel control moves to increase speed when it is in the running position. This is difficult to explain and therefore to better understand the concept you should watch the third part of the video.

A pulsating air-breathing engine (PuARE) is one of the three main types of air-breathing engines (PRE), the peculiarity of which is the pulsating mode of operation. The pulsation creates a characteristic and very loud sound, by which these motors are easily recognized. Unlike other types of power units, the PuVRD has the most simplified design and low weight.

Structure and principle of operation of the PuVRD

A pulse jet engine is a hollow channel, open on both sides. On one side - at the inlet - there is an air intake, behind it there is a traction unit with valves, then there is one or more combustion chambers and a nozzle through which the jet stream exits. Since engine operation is cyclical, its main cycles can be distinguished:

• the intake stroke, during which the inlet valve opens and air enters the combustion chamber under the influence of vacuum. At the same time, fuel is injected through the injectors, resulting in the formation of a fuel charge;
• the resulting fuel charge is ignited by a spark from the spark plug, and during the combustion process gases with high pressure, under the influence of which the inlet valve closes;
• when the valve is closed, combustion products exit through the nozzle, providing jet thrust. At the same time, a vacuum is formed in the combustion chamber when exhaust gases exit, the inlet valve automatically opens and lets a new portion of air inside.

The engine inlet valve may have different designs And appearance. Alternatively, it can be made in the form of blinds - rectangular plates mounted on a frame, which open and close under the influence of differential pressure. Another design is shaped like a flower with metal “petals” arranged in a circle. The first option is more efficient, but the second is more compact and can be used on small-sized structures, for example, in model aircraft.

Fuel is supplied by injectors that have check valve. When the pressure in the combustion chamber decreases, a portion of fuel is supplied, but when the pressure increases due to combustion and expansion of gases, the fuel supply stops. In some cases, for example, on low-power model aircraft engines, there may be no injectors, and the fuel supply system resembles a carburetor engine.

The spark plug is located in the combustion chamber. It creates a series of discharges, and when the concentration of fuel in the mixture reaches desired value, the fuel charge ignites. Since the engine has small sizes, its walls, made of steel, quickly heat up during operation and can ignite the fuel mixture no worse than a candle.

It is not difficult to understand that in order to start a PURD engine, an initial “push” is needed, during which the first portion of air enters the combustion chamber, that is, such engines require preliminary acceleration.

History of creation

The first officially registered developments of PuVRDs date back to the second half of the 19th century. In the 60s, two inventors independently of each other managed to obtain patents for new type engine. The names of these inventors are N.A. Teleshov. and Charles de Louvrier. At that time, their developments did not find wide application, but already at the beginning of the twentieth century, when they were looking for a replacement for piston engines for aircraft, German designers paid attention to PuVRDs. During World War II, the Germans actively used the FAU-1 projectile aircraft equipped with a PuVRD, which was explained by the simplicity of the design of this power unit and its low cost, although its performance characteristics were inferior even to piston engines. This was the first and only time in history that this type of engine was used in mass production of aircraft.

After the end of the war, PuVRDs remained “in military affairs”, where they found use as a power unit for air-to-surface missiles. But here, too, over time they lost their position due to speed restrictions, the need for initial overclocking and low efficiency. Examples of using PuVRDs are Fi-103, 10X, 14X, 16X, JB-2 missiles. IN last years There is a renewed interest in these engines, new developments are appearing aimed at improving them, so, perhaps, in the near future, PuVRDs will once again become in demand in military aviation. On this moment The pulse jet engine is brought back to life in the field of simulation, thanks to the use of modern construction materials in the design.

Features of PuVRD

The main feature of the PuVRJE, which distinguishes it from its “close relatives” turbojet (TRJ) and ramjet engines (RAMJET), is the presence of an intake valve in front of the combustion chamber. It is this valve that does not allow combustion products to pass back, determining their direction of movement through the nozzle. In other types of engines there is no need for valves - there the air enters the combustion chamber already under pressure due to pre-compression. This, at first glance, insignificant nuance plays a huge role in the operation of the thruster from the point of view of thermodynamics.

The second difference from turbojet engines is the cyclical operation. It is known that in a turbojet engine the fuel combustion process occurs almost continuously, which ensures smooth and uniform jet thrust. The PURD works cyclically, creating vibrations inside the structure. To achieve maximum amplitude, it is necessary to synchronize the vibrations of all elements, which can be achieved by selecting required length nozzles

Unlike a ramjet engine, a pulsejet engine can operate even at low speeds and being in a stationary position, that is, when there is no oncoming air flow. True, its operation in this mode is not capable of providing the amount of jet thrust required for launch, so aircraft and missiles equipped with a ramjet engine require initial acceleration.

A small video of the launch and operation of the PuVRD.

Types of PuVRD

In addition to the usual PURD in the form of a straight channel with an inlet valve, as described above, there are also its varieties: valveless and detonation.

Valveless PuVRD, as its name suggests, does not have an inlet valve. The reason for its appearance and use was the fact that the valve is a rather vulnerable part that very quickly fails. In the same version, the “weak link” is eliminated, and therefore the service life of the motor is extended. The design of the valveless PuVRD is shaped like the letter U with the ends directed backward along the direction of the jet thrust. One channel is longer, it is “responsible” for traction; the second is shorter, air enters the combustion chamber through it, and during combustion and expansion of the working gases, some of them exit through this channel. This design allows for better ventilation of the combustion chamber, prevents leakage of the fuel charge through the inlet valve and creates additional, albeit insignificant, thrust.

without valve version PuVRD
without valve U-shaped PuRVD

Detonation PuVRD involves burning a fuel charge in detonation mode. Detonation involves a sharp increase in the pressure of combustion products in the combustion chamber at a constant volume, and the volume itself increases as gases move through the nozzle. In this case, the thermal efficiency of the engine increases in comparison not only with a conventional PURD, but also with any other engine. At the moment, this type of motor is not in use, but is at the stage of development and research.

detonation PuRVD

Advantages and disadvantages of PuVRD, scope of application

The main advantages of pulsating air-breathing engines can be considered their simple design, which makes them low cost. It is these qualities that have led to their use as power units on military missiles, unmanned aircraft, flying targets, where it is not durability and super speed that are important, but the ability to install a simple, light and cheap motor capable of developing the required speed and delivering the object to the target. These same qualities made the PuVRD popular among aircraft modeling enthusiasts. Lightweight and compact engines, which, if desired, can be made independently or purchased reasonable price, perfect for model airplanes.

PuVRD has many disadvantages: increased level noise during operation, uneconomical fuel consumption, incomplete combustion, limited speed, vulnerability of some structural elements, such as the inlet valve. But, despite such an impressive list of disadvantages, PuVRDs are still indispensable in their consumer niche. They - perfect option for “one-time” purposes, when there is no point in installing more efficient, powerful and economical power units.

The most difficult thing to manufacture and the most important for the operation of the turbine is the compressor stage. It usually requires precision CNC machining tools or manual drive. Luckily, the compressor operates at low temperatures and can be 3D printed.

Another thing that is usually very difficult to replicate at home is what is called a "nozzle vane" or simply NGV. Through trial and error, the author found a way to do this without using welding machine or other exotic instruments.

What you will need:
1) 3D printer capable of working with PLA filament. If you have an expensive one like an Ultimaker that's great, but a cheaper one like a Prusa Anet will work too;
2) You must have enough PLA to print all the parts. ABS is not suitable for this project as it is too soft. You can probably use PETG, but this has not been tested, so do so at your own risk;
3) Can appropriate size (diameter 100 mm, length 145 mm). Preferably the jar should have a removable lid. You could use a regular jar (say, pineapple chunks), but then you'll need to make one for it. metal cover;
4) Galvanized iron sheet. A thickness of 0.5 mm is optimal. You can choose a different thickness, but you may have difficulty bending or sanding, so be prepared. In any case, you will need at least a short strip of galvanized iron 0.5 mm thick to make the spacer for the turbine casing. 2 pieces will do. Size 200 x 30 mm;
5) Stainless steel sheet for making turbine wheel, NGV wheel and turbine casing. Again, a thickness of 0.5 mm is optimal.
6) Solid steel rod for making turbine shaft. Beware: mild steel just doesn't work here. You will need at least some carbon steel. Hard alloys will be even better. The shaft diameter is 6 mm. You can choose a different diameter, but then you will need to find suitable materials for making a hub;
7) 2 pcs. 6x22 bearings 626zz;
8) 1/2" pipes 150 mm long and two end fittings;
9) drilling machine;
10) Sharpener
11) Dremel (or something similar)
12) Metal hacksaw, pliers, screwdriver, M6 die, scissors, vice, etc.;
13) a piece of copper or stainless steel pipe for spraying fuel;
14) A set of bolts, nuts, clamps, vinyl tubes and other things;
15) propane or butane torch

If you want to start the engine, you will also need:

16) Propane tank. There are gasoline or kerosene engines, but getting them to run on these fuels is a bit difficult. It's better to start with propane and then decide if you want to switch to liquid fuel or if you're already happy gas fuel;
17) A pressure gauge capable of measuring pressure of several mm of water.
18) Digital tachometer for measuring turbine speed
19) Starter. To start a jet engine you can use:
Fan (100 W or more). Better centrifugal)
electric motor (100W or more, 15000rpm; you can use your Dremel here).

Making a hub

The hub will be made from:
1/2" pipe 150 mm long;
two 1/2" hose fittings;
and two bearings 626zz;
Using a hacksaw, cut off the herringbones from the fittings, and use a drill bit to enlarge the remaining holes. Insert the bearings into the nuts and screw the nuts onto the pipe. The hub is ready.

Making a shaft

Theory (and experience to some extent) says that it makes no difference whether you make a shaft from mild steel, hard steel or stainless steel. So choose the one that is more accessible to you.

If you expect to get decent thrust from the turbine, it is better to use a steel rod with a diameter of 10 mm (or larger). However, at the time of writing, the shaft was only 6 mm.

Cut an M6 thread on one side to a length of 35 mm. Next, you need to cut the thread from the other end of the rod so that when the rod is inserted into the hub (the bearings rest against the end of the pipe are tightened using the nuts that you made from hose fittings) and when the lock nuts are screwed to the end of the thread on both sides, between the nuts and bearings leave a small gap. This is a very complicated procedure. If the thread is too short and the longitudinal play is too large, you can cut the thread a little further. But if the thread seems too long (and there is no longitudinal play at all), it will be impossible to fix it.

As an option, rollers from a laser printer are exactly 6 mm in diameter. Their disadvantage is that their limit is 20-25000 rpm. If you want higher speeds, use thicker rods.

3D printing of turbine wheel and NGV dies

For the manufacture of a turbine wheel, or rather its blades, press dies are used.
The shape of the blade becomes smoother if you press the blade not to the final shape in one step (pass), but to some intermediate shape (1st pass) and only then to the final shape (2nd pass). Therefore, there is an STL for both types of press dies. For the 1st pass and for the second.

Here are the STL matrix files for the NGV wheel and the STL files for the turbine wheel matrices:

Manufacturing of impellers

This design uses 2 types of steel wheels. Namely: turbine wheel and NGV wheel. Stainless steel is used for their manufacture. If they were made of lightweight or galvanized material, they would barely be enough to show how the engine works.

You can cut the discs out of sheet metal and then drill a hole in the center, but most likely you won't hit the center. Therefore, drill a hole in a sheet of metal, and then glue the paper template so that the hole in the metal and the hole in the paper template coincide. Cut the metal according to the template.

Drill auxiliary holes. (Note that the center holes should already be drilled. Also note that the turbine wheel only has a center hole.)

It's also a good idea to leave a little allowance when cutting the metal and then sharpen the edge of the discs using a drill press and a sharpener.
At this point it may be better to make several backup drives. It will become clear why later.

Blade formation

Sliced ​​discs are difficult to fit into the molding die. Use pliers to turn the blades slightly. Discs with pre-twisted blades are much easier to form with dies. Place the disk between the halves of the press and squeeze it in a vice. If the dies were pre-lubricated with machine oil, everything will go much easier.

The vice is a fairly weak press, so you'll likely need to hit the assembly with a hammer to compress it further. Use several wooden pads to avoid breaking the plastic dies.

Two-step shaping (using 1st pass matrices and 2nd pass matrices to finalize the shape) gives definitely better results.

Making a support

The document file with the template for the support is here:

Cut a piece from a stainless steel sheet, drill required holes and bend the piece as shown in the photos.

Making a set of metal spacers

If you had a lathe, you could make all the spacers on it. Another way to do this is to cut several flat disks from a sheet of metal, stack them on top of each other, and bolt them tightly together to create a three-dimensional piece.

Use a 1mm thick mild (or galvanized) steel sheet here.

Documents with templates for spacers are here:

You will need 2 small disks and 12 large ones. The quantity is given for a sheet of metal 1 mm thick. If you use a thinner or thicker one, you will need to adjust the number of discs to get the correct overall thickness.
Cut the discs and drill holes. Grind discs of the same diameter as described above.

Support washer

Since the backing washer holds the entire NGV assembly, you must use thicker material here. You can use a suitable steel washer or sheet (black) of at least 2mm thickness.

Template for support washer:

Assembling the NGV Interior

You now have all the parts to assemble the NGV. Install them onto the hub as shown in the photos.

The turbine needs some pressure to operate properly. And in order to prevent the free spread of hot gases, we need a so-called “turbine casing”. Otherwise, the gases will lose pressure immediately after passing through the NGV. For proper functioning, the casing must match the turbine + a small gap. Since our turbine wheel and NGV wheel are the same diameter, we need something to provide the necessary clearance. This something is a turbine casing spacer. It's simply a strip of metal that wraps around the NGV wheel. The thickness of this sheet determines the size of the gap. Use 0.5mm here.

Simply cut a strip 10 mm wide and 214 mm long from a sheet of any steel with a thickness of 0.5 mm.

The turbine casing itself will be a piece of metal, the diameter of the NGV wheel. Or better yet, a couple of pieces. Here you have more freedom in choosing the thickness. The casing is not just a strip because it has attachment tabs.

The documentation file with the template for the turbine casing is here:

Place the shroud spacer onto the NGV blades. Secure with steel wire. Find a way to secure the spacer so it doesn't move when the wire is removed. You can use soldering.

Then remove the wire and screw the turbine casing onto the spacer. Use the wire again to wrap tightly.

Do as shown in the photos. The only connection between the NGV and the hub is three M3 screws. This limits the heat flow from the hot NGV to the cold hub and prevents the bearings from overheating.

Check if the turbine can rotate freely. If not, align the NGV housing by changing the position of the adjusting nuts on the three M3 screws. Adjust the tilt of the NGV until the turbine can rotate freely.

Making a combustion chamber

Paste this template over the metal sheet. Drill holes and cut the shape. There is no need to use stainless steel here. Roll into a cone. To prevent it from unfolding, bend it.
The front of the camera is here:

Use this template again to make a cone. Use a chisel to make wedge slits and then roll into a cone. Secure the cone with a bend. Both parts are held together only by friction from the engine. Therefore, you don’t need to think about how to secure them at this stage.

Working wheel

The impeller consists of two parts:
disk with blades and casing

This is a Kurt Schreckling impeller that has been heavily modified by me to be more tolerant of longitudinal movement. Note the labyrinth that prevents air from returning due to back pressure. Print both parts and glue the cover onto the disc with the blades. Good results can be obtained using acrylic epoxy resin.

Compressor stator (diffuser)

This item is very complex shape. And when other parts can (at least in theory) be made without the use of precision equipment, this is impossible. To make matters worse, this part has the greatest impact on the compressor's efficiency. This means that whether the entire engine will work or not is highly dependent on the quality and precision of the diffuser. That's why don't even try to do it manually. Do this on the printer.

For ease of 3D printing, the compressor stator is divided into several parts. Here are the STL files:

3D print and assemble as shown in the photos. Please note that the nut is pipe thread The 1/2" should be attached to the central compressor stator housing. This is used to hold the bushing in place. The nut is secured with 3 M3 screws.
Template for where to drill holes in the nut:

Also note the aluminum foil heat protection cone. It is used to prevent PLA parts from softening due to thermal radiation from the combustion liner. You can use any beer can as a source of aluminum foil here.

You will need a tin can that is 145mm long and 100mm in diameter. It's better if you can use a jar with a lid. Otherwise you will need to install the NGV with the hub in the bottom of the tin and you will have additional problems assembling the engine for servicing.

Cut off one bottom of the tin can. In another bottom (or better in the lid) cut round hole 52 mm. Then cut its edge into sectors as shown in the photographs.

Insert the NGV assembly into the hole. Wrap the sectors tightly with steel wire.

Make a ring from a copper tube ( outside diameter 6 mm, inner diameter 3.7 mm). Or better you can use stainless steel tubes. The fuel ring should fit snugly against the internal components of your canner. Solder it.
Drill the fuel injectors. These are just 16 pieces of 0.5 mm holes, evenly distributed around the ring. The direction of the holes should be perpendicular to the air flow. Those. need to drill holes in inside rings.

Please note that the presence of so-called "hot spots" in the engine exhaust depends almost exclusively on the quality of the fuel ring. Dirty or uneven bores and you'll end up with an engine that simply destroys itself when you try to start it. The presence of hot spots depends much less on the quality of the liner than others try to say. But the fuel ring is very important.

Check the quality of fuel spray by igniting it. The flames should be equal to each other.

Once completed, install the fuel injector into the can body.

All you need to do at this stage is put all the pieces together. If things go well, this won't be a problem.

Seal the lid of the can with a heat-resistant sealant; you can use silicate glue with a heat-resistant filler. You can use graphite dust, steel powder and so on.

After the engine is assembled, check that the rotor rotates freely. If so, do a preliminary fire test. Use some one enough powerful fan to blow out the air intake or simply rotate the shaft with a dremel. Lightly turn on the fuel and ignite the flow at the rear of the engine. Adjust the rotation to allow the flame to enter the combustion chamber.

NOTE: At this stage you are not trying to start the engine! The only purpose of a fire test is to heat it up and see if it behaves well or not. At this point, you can use a butane cylinder, which is usually used for hand torches. If everything is fine you can move on to the next step. However, it is better to seal the engine with oven sealant (or silicate glue filled with a small amount of heat-resistant powder).

You can start the engine either by blowing air into it or by rotating its shaft with some kind of starter.
Be prepared to burn a few NGV drives (and possibly turbines) when attempting to start. (This is why it was recommended in step 4 to make some backups.) Once you get comfortable with the engine, you should be able to start it at any time without any problems.

Please note that the engine may currently serve primarily educational and entertainment purposes. But this is a fully functional turbojet engine, capable of spinning to any desired speed (including self-destructive speed). Feel free to improve and modify the design to suit your purposes. First of all, you will need a thicker shaft to achieve higher RPM and therefore traction. The second thing to try is to wrap the outside of the engine metal pipe- fuel line and use it as an evaporator for liquid fuel. This is where the hot wall motor design comes in handy. Another thing to think about is the lubrication system. In the simplest case, this might take the form of a small bottle with a small amount of oil and two pipes - one pipe to relieve the pressure from the compressor and direct it to the cylinder, and the other pipe to direct the oil from the pressurized cylinder and direct it to the rear beam. Without lubrication, the engine can only run for 1 to 5 minutes depending on the NGV temperature (the higher the temperature, the shorter the running time). After this, you need to lubricate the bearings yourself. And with the added lubrication system, the engine can run for a long time.

The valveless pulsating engine is the world's simplest jet engine. Its development was unfortunately suspended with the widespread use of turbojet engines, but it continues to be of interest to hobbyists, as it can be built in a home workshop. I built my engine by studying Lockwood's patent, according to which the device can be of any size, as long as certain proportions are observed. The engine has no moving parts, it can also run on any fuel if it is evaporated before entering the combustion chamber (I used a mixture of gasoline and diesel fuel in equal parts), but the start occurs on gas (this is much easier). The design is simple and relatively inexpensive to replicate. I don’t know with what frequency explosions occur in the combustion chamber of my engine, but I guess that this happens about 30-50 times per second, the operation of the device is accompanied by very loud noise. I hope to measure this frequency someday.

The engine runs on propane, which enters the combustion chamber through a long metal tube, at the end of which there is a sprayer that helps evaporate the liquid fuel. When propane is used a nebulizer is not necessary, in my case the gas comes directly through a 4mm ID tube. The tube is connected to the combustion chamber with a 10mm fitting. I have three of these tubes made - one for propane, the other two for diesel fuel and kerosene.

During the starting process, propane is supplied to the combustion chamber, and then just one spark at the plug is enough for the engine to start.

According to the patent, such an engine of any size can be built. My drawing shows my version of the device, which differs slightly from the design of the exhaust pipe proposed in the patent, which simplifies manufacturing, however, since I did not measure the thrust, this may have affected the efficiency. Flow straighteners usually double the thrust and I'm going to try making one.

Abbreviations in the drawing:

• NL - nozzle length
• NM—nozzle diameter
• CL - Combustion chamber length
• CM - combustion chamber diameter
• TL - Tail tube length
• TM - Tail pipe diameter

Gas cylinders can be bought anywhere, I chose an 11-kilogram one with an industrial connector. I did not use any reducers, I simply installed a needle valve, since the gas flow is quite large and a regular reducer will not give the required flow. The chance that the propane in the tube and tank will catch fire is very small if the tank is not completely emptied. In the pictures below you can see what it looks like.

The spark plug is screwed into a specially made lathe part welded into the combustion chamber. You can use any spark plug, I installed an NGK BP6E S without additional resistance, and used a bobbin from an old car. I also did electronic circuit to obtain a spark, which must be obtained only once, at the moment the engine starts.

The pipe body is welded from three-millimeter 316L stainless steel. I didn’t know how to calculate the thickness, and just took a thicker sheet, with a margin. The engine was started many times and no problems were found.